Printed circuit boards are an increasingly common component in all types of electronic devices. Electronic circuit boards are easy and inexpensive to manufacture, install and use. By eliminating the need for a "spaghetti bowl" of hard wire connections, complex electronic equipment can be made less expensively and much more compactly.
Printed circuit boards generally comprise a board constructed from an insulating material such as a glass-fiber-reinforced epoxy resin. The board can be rigid or it can be relatively flexible. Onto the board are formed by "printing" techniques, a plurality of electrically conductive circuitry tracks. These tracks are then connected to various electrical components which are affixed to the board.
It is common practice in the industry to conduct an integrity test on each newly manufactured printed circuit board to be sure there are no broken or disconnected circuits on the board. The testing procedure entails making electrical contact between a number of predetermined locations on the printed circuitry and specially adapted electrical diagnostic equipment which measures an integrity parameter at each predetermined location and compares it to a standard value.
Contacting the various points along the electronic circuitry is typically accomplished by placing the printed circuit board on a test fixture device and bringing the circuitry into contact with a plurality of test probes, each of which is electrically connected to the diagnostic equipment. An electrical charge is applied at points along the circuitry and the resulting electrical characteristics at each of the predetermined locations are measured using the probes and compared by the diagnostic equipment with the standard values.
It is also frequently desirable to test the functionality of the completed circuit board. In a functionability test, a second, smaller number of test probes are placed into contact with the input, the output, and a selected set of predetermined locations along the printed circuitry. An electrical current is applied to the input points and the functional aspects of the circuitry are measured by a second kind of electrical diagnostic equipment.
Heretofore, it has been necessary to conduct the integrity test and the functionality test with two separate sets of test probes, generally in two separate test fixtures. It would be highly desirable, however, if these two different tasks could be accomplished on a single test fixture. This would cut both the cost of the testing equipment and the time involved in the testing procedure by at least fifty percent.